With the continuous development of the mobile communication technology, the total data transmission rate from system perspective is increasing sharply. However, due to the larger interference of neighbor cells, the performance of cell edge user equipment (UE) is difficult to be improved greatly. This is also becomes a bottleneck of the increase of the data transmission rate. Many researches, being discussed by the 3GPP organization currently, in the LTE technology are related to the improvement of the performance of the edge UE, for example, coordinated multipoint transmission (CoMP), enhanced inter-cell interference cancellation (eICIC, like almost blank subframe, ABS), receiver based on network-assisted interference cancellation and/or suppression (NAICS), etc. The NAICS receiver is mainly implemented on UE side, and the UE detects the signals sent by one or more heavily interfering cells to achieve the purpose of canceling these interference signals and thus improving the cell edge UE's performance.
NAICS receivers, being discussed and researched by the 3GPP organization currently, have a plurality of directions. However, considering the tradeoff between performance gain and the implementation complexity of receivers, manufacturers are more inclined to the interference symbol level detection. For example, symbol level maximum likelihood (SLML) receiver and symbol level interference cancellation (SLIC) receiver, the performance gain of which has been confirmed by all the manufacturers in the working group RAN4, have become NAICS receiver solutions having the highest development potential in Release 12.
In such NAICS receiver solutions, interference signals of neighboring cells may be detected only after UE acquires the related information about the neighboring cells. Such information is mainly classified into two types: one type is static scheduling information, i.e., parameter which will not change within a certain time period, for example, control format indicator (CFI), multimedia broadcast multicast service single frequency network (MBSFN) configuration, cell-specific reference signal (CRS) configuration, channel state information reference signal (CSI-RS) configuration, system bandwidth, cell identity (ID), cell-specific parameter P_B associated with the downlink transmission power allocation, etc.; while the other type is dynamic scheduling information, i.e., parameters which are likely to vary in each subframe, for example, modulation and coding scheme (MCS), transmission mode (TM), rank indicator (RI), precoding matrix indicator (PMI), UE-specific parameter P_A associated with the downlink transmission power allocation, and the allocation information of physical downlink shared channel (PDSCH), etc.
The dynamic scheduling information mentioned above has been described in LTE standards as below.
a) 10 transmission modes have been listed in the LTE standard Release 11. Transmission mode 1: transmission through a single antenna port of eNodeB; transmission mode 2: transmission diversity; transmission mode 3: open-loop spatial multiplexing; transmission mode 4: closed-loop spatial multiplexing; transmission mode 5: multi-user multiple input multiple output (MU-MIMO); transmission mode 6: closed-loop spatial multiplexing with rank 1; transmission mode 7: transmission using UE-specific reference signals (a single antenna port); transmission mode 8: transmission using UE-specific reference signals (up to two antenna ports); transmission mode 9: transmission using UE-specific reference signals (up to eight antenna ports); and, transmission mode 10: transmission using UE-specific reference signals (for CoMP transmission).
b) There are 32 types of MCSs defined in the standards: MCS0, MCS1, . . . , MCS31, where MCS0-MCS9 refer to QPSK transmission, MCS10-MCS16 refer to 16 QAM transmission, MCS17-MCS28 refer to 16 QAM transmission, and MCS29-MCS31 are used for retransmission.
c) For RI and PMI, up to 8 layers transmission is supported in the current standards. Particularly, for two antenna ports transmission, PMI={0, 1, 2, 3} for RI=1; and PMI={ 1, 2} for RI=2. For four antenna ports transmission, RI could be { 1, 2, 3, 4}, and there are 16 types of optional PMIs, PMI={0, 1, 2, . . . , 15}.
d) For parameter P_A, there are 8 optional values {−6 dB, −4.77 dB, −3 dB, −1.77 dB, 0 dB, 1 dB, 2 dB, 3 dB} defined in the standards.
In NAICS standardization progress, 3GPP working groups RANI and RAN4 are mainly inclined to two solutions on how UE acquires the dynamic scheduling information:
a) One solution is using dynamic signaling indicators. This solution has the advantage of low UE implementation complexity and the apparent disadvantages that the signaling overhead is very large and base stations need to exchange a large amount of real-time information;
b) The other solution is performing blind detection to obtain these dynamic parameters totally by the UE itself. This solution doesn't introduce any additional signaling overhead, but requires high UE implementation complexity with a lot of blind detection parameters combinations.
This solution, where these dynamic parameters are blindly detected without additional signaling overhead, has the disadvantages that the UE implementation complexity is extremely high and there are a large number of parameter combinations to be blindly detected (the parameters combinations amount is at least the exponential of the total number of modulation constellation, where the exponential is the number of RI and PMI combinations).
In addition, when these dynamic parameters are configured with some values, for example, when the interference is a multi-layer transmission with high-order modulation scheme like 64 QAM, the NAICS receiver cannot achieve good interference signal blind detection performance and interference cancellation/suppression performance.
Therefore, it is very necessary to provide effective technical solutions to solve the problem that NAICS receiver cannot achieve good interference signal blind detection performance and interference cancellation/suppression performance.